The subject matter described herein relates generally to controlling operation of electric power converters, and more specifically, to removing heat from a semiconductor device.
Many known semiconductor devices are used for electric power conversion, e.g., rectifiers and inverters. Most known rectifiers are used for converting alternating current (AC) to direct current (DC) and most know inverters are used for converting DC current to AC current. Some of these rectifiers and inverters are integrated into full power conversion assemblies, i.e., power converters, used in renewable electric power generation facilities that include solar power generation farms and wind turbine farms. However, variables such as solar intensity and wind direction and speed typically produce electric power having varying voltage and/or frequency. Power converters may be coupled between the electric power generation devices in the generation facilities and an electric utility grid. Each power converter receives generated electric power from the associated generation device and transmits electricity having a fixed voltage and frequency for further transmission to the utility grid via a transformer. The transformer may be coupled to a plurality of power converters associated with the electric power generation facility.
Known semiconductor devices include insulated gate bipolar transistors (IGBTs), gate turn-off thyristors (GTOs), silicon-controlled rectifiers (SCRs), metal oxide semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), and diodes. Such IGBTs and GTOs generate heat when placed in service. Many known heat removal systems for such semiconductors include a path for heat flow with a high thermal resistance, thereby resulting in a high operating junction temperature for a particular amount of power loss in the semiconductor device. For example, the cooling path for many IGBT modules includes a semiconductor die soldered onto one side of an electrically-isolating substrate, e.g., aluminum nitride, thereby forming an electrical junction thereon. Most of the heat generated by the IGBT is channeled from the junction side of the electrically-isolating substrate, through the substrate, to the opposite side. Many such known substrates include a heat transfer mechanism on the side opposite the junction. This heat transfer mechanism is typically referred to as single-side cooling.
Generally, such electrically-isolating substrates have a relatively high thermal resistance, and this thermal resistance induces the semiconductor die temperature on the junction side of the substrate to be higher than the opposite side of the substrate with the heat transfer mechanism. Also, typically, the thermal path to the heat transfer mechanism includes additional layers of materials that have a high thermal resistance. Such materials include a layer of solder below the electrically-isolating substrate, a layer of copper, a heat sink, and an interface of silicon grease between the IGBT module and the heat sink, wherein these thermal resistances also retard the transfer of heat from the IGBT.